Camming system including a flexible cam of adjustable peripheral length

ABSTRACT

A camming system which includes a cam carrier supporting a flexible cam of selectively adjustable peripheral length. The carrier and a sensor for sensing the cam when it is proximate the sensor are mounted for motion relative to each other along a predetermined path. A guide track on the carrier supports the cam with at least a portion of the cam exposed to and facing toward the sensor to be sensed thereby. A hub mounted on the carrier is attached to one end of the cam and may be rotated to wind and unwind the cam so that it extends for a selectively variable peripheral length along the guide track.

[451 May 27, 1975 1' CAMMING SYSTEM INCLUDING A FLEXIBLE CAM OFADJUSTABLE PERIPHERAL LENGTH [75] Inventors: Robert B. Costa, Covina;Edward M. Troup, Mt. Baldy, both of Calif.

[73] Assignee: Clemar Manufacturing Corporation,

Glendora, Calif.

[221 Filed: Nov. 8, 1973 [21] Appl. No.: 413,885

[52] U.S. Cl 74/568 R; 74/568 FS; 74/568 T; 200/38 CA [51] Int. Cl. Fl6h53/00 [58] Field of Search 74/568 FS, 568 M, 568 T, 74/568 R; 200/38 CA[56] References Cited Condon et al. 74/568 R X Cole 74/568 M PrimaryExaminer-Samuel Scott Assistant ExaminerF. D. Shoemaker Attorney, Agent,or F irm-Fulwider, Patton, Rieber, Lee, & Utecht [57] ABSTRACT A cammingsystem which includes a cam carrier supporting a flexible cam ofselectively adjustable peripheral length. The carrier and a sensor forsensing the cam when it is proximate the sensor are mounted for motionrelative to each other along a predetermined path. A guide track on thecarrier supportsthe cam with at least a portion of the cam exposed toand facing toward the sensor to be sensed thereby: A hub mounted on thecarrier is attached to one end of the cam and may be rotated to wind andunwind the cam so that it extends for a selectively variable peripherallength along the guide track.

17 Claims, 8 Drawing Figures CAMMING SYSTEM INCLUDING A FLEXIBLE CAM OFADJUSTABLE PERIPHERAL LENGTH BACKGROUND OF THE INVENTION This inventionrelates to a cam assembly incorporating a flexible cam, the peripherallength of which may be selectively adjusted to vary the range of camoperation.

In performing timing or positioning functions, it is well known toutilize systems involving mechanical cams. Such systems typicallyincorporate a cam carrier which supports the cam for motion in relationto a sensor which senses the cam. The sensor provides an output whichvaries dependent on whether the cam is proximate to the sensor or hasmoved beyond it. In applications where the control function performed bythe cam may need to be changed from time to time, it is known to providefor adjustment of the range of cam operation relative to the carrier,for example, by positioning of clips at selectively variable spacingsaround the periphery of the carrier or by attaching projecting portionson the carrier.

One prior cam assembly disclosed in U.S. Pat. No.

3,678,780, issued July 25, 1972 to Ivor Ponting, discloses a camassembly including a cam carrier in the form of a serrated cylindricalbody provided with bosses at its opposite axial ends upon which arerotationally mounted two segmental cams provided with inwardlyprojecting resilient portions which engage the body serrations to act asdetents. Two adjacent shoulders on the cams are spaced apart to definean in-dwell region of reduced peripheral radius while the remainingregion of the two cams overlap to provide an outdwell region of greaterradius extending around the remainder of the periphery. The in-dwellregion may be adjusted in its length relative to the total periphery byturning the cam segments relative to. each other on the carrier body.

Although satisfactory for its intended purpose, suc a prior cam assemblymay have some disadvantages. For example, such a cam assembly providesfor only a single adjustable control function on the one cam carrier,whereas, for certain applications, it may be essential to mount aplurality of separate, individually adjustable cams of differingperipheral length on a single cam carrier.

In addition, in such a prior cam assembly, the indwel] region isnecessarily of a curved configuration centered on the radius of rotationof the cam carrier, whereas, under certain circumstances, it may bedesirable to have an adjustable cam which is straight or has a curvaturegreater or less than the radius of curvature about the axis of movementof the cam carrier. Additionally, such a prior cam assembly whichutilizes cam segments mounted at opposite axial ends of the carrier maycause chanting of a mechanical cam follower because the cam segments arelaterally separated due to their mounting at opposite ends of the camcarrier.

SUMMARY OF THE INVENTION plurality of the adjustable flexible, cams maybe mounted on a single carrier to provide a sequence of controlfunctions of differing duration during a single cycle of movement of thecam carrier relative to the sensor. Each adjustable cam may beseparately adjusted to vary its peripheral length relative to thecarrier without requiring any change in the adjustment of the peripherallength of the other cams on the carrier. The cam assembly of theinvention therefore enables a single cam carrier to support a pluralityof separately adjustable cams for selective and individual variation ofcontrol functions.

In another aspect of the invention, each cam, when it is used inassociation with a mechanical cam follower, can be positioned tomaintain a uniform centered relation of the follower on the cam followerduring the complete path of travel of the cam past the follower. Withsuch an arrangement there is no tendency to impose side or tiltingforces on the cam follower which might introduce error into theoperation of the associated sensing equipment.

In more detail, the carrier is provided with an elongate guide track.The cam comprises an elongate flexible wall having opposite longitudinaledges. The guide track slidably engages at least one of the edges tosupport the wall relative to the carrier extending along the guide trackwith at least a portion of the wall surface to and facing towards thesensor to be sensed thereby. A hub is fixedly secured to onelongitudinal end of the flexible wall and is mounted on the carrier forrotation about an axis parallel to the wall surface. By rotation of thehub the wall may be wound and unwound along the guide track to vary theperipheral extent to which it is exposed to the sensor.

The sensor may sense the cam in a variety of ways including mechanicalcontact, photoelectric sensing, fluid pressure, magnetic sensing, anddetection of radioactivity.

The hub and its connection to the carrier incorporate resilient detentportions so that once the hub has been turned to 'set the cam length ata preselected value, the detents maintain the setting during operation.

The foregoing, and other advantages and features of the invention aredescribed more fully in the detailed description which follows.

BRIEF DESCRIPTION OF THE DRAWINGS A camming system according to certainpreferred embodiments of the invention is illustrated in theaccompanying drawings in which:

FIG. 1 shows a camming system including a rotary cam carrier whichcarries a plurality of cam assemblies, each contructed according to thepreferred embodiment of the invention, past a sensor;

FIG. 2 is a cross-sectional side view on an enlarged scale through a hubportion of one of the cam assemblies shown in FIG. 1;

FIG. 3 is a perspective view of an adjustable cam forming a part of theassembly shown in FIG. 2',

FIG. 4 is a top view of the adjustable cam shown in FIG. 3;

FIG. 5 is a cross-sectional view of a portion of the cam assembly shownin FIG. 2 taken along the line 5-5 therein, illustrating certain detentportions thereof in an engaged condition;

FIG. 6 is a further view of the detent portions shown in FIG. 5 when atorque is applied to force the detent portions apart during adjustmentof the cam assembly; and

FIGS. 7 and 8 show a second embodiment of the invention wherein the camassembly is mounted on a stationary carrier and a sensor is moved in astraight linear direction past the adjustable cam assembly.

DETAILED DESCRIPTION Referring to FIG. 1 of the drawings, a plurality ofadjustable cam assemblies 2, each constructed according to the preferredembodiment of the invention, are shown mounted on a rotary cam carrier4. The cam carrier, which rotates in an anticlockwise direction, carriesthe adjustable cam assemblies 2 consecutively past a sensor 6 which isactivated and deactivated, thereby performing control functions.

The rotary cam carrier 4 can be, for example, a station timer of thetype forming part of the Timing Unit For Connecting Power SequentiallyTo A Plurality Of Stations" disclosed in the patent application ofNorman A. Morgan, filed concurrently with the present application andassigned to the same assignee. The timing system disclosed in thatapplication is utilized to control the operation of a sprinkler systemhaving a number of sprinklers which are to be actuated in cycles ofoperation in which each sprinkler is operated sequentially during eachcycle for a period which is separately and individually adjustable foreach sprinkler. However, it is to be realized that the adjustable cam ofthe present invention is in no way confined to use in timing systems.For example, instead of operating a cam follower to perform a timingcontrol function, the adjustable cams 2 could be utilized to perform apositioning function such as displacing a valve actuator controllingflow of liquid through a controlled system. Moreover, it is notnecessary that the adjustable cams be mounted on a rotary cam carrier.Additionally, it would be possible to utilize the adjustable camassembly of the invention in a system wherein the cam remains stationarywhile a plurality of sensors moves sequentially past the cam.

However, for ease of description, the cam assembly according to thefirst embodiment of the invention, will be described primarily withreference to use in a system involving the rotary cam carrier 4 utilizedfor controlling a sensor 6 to perform functions. In the embodiment shownin FIG. 1 the sensor is an electrical switch 7 having a pivoted finger 8extending in a direction generally tangentially to the cam carrier 4. Atits free end the finger 8 includes a radially extending portion which isbiased in a direction radially towards the center of rotation of the camcarrier by a spring biased plunger 12 controlling the on-off operationof the switch 7.

Each adjustable cam assembly 2 includes an adjustable cam 14 (FIG. 3)formed of resiliently flexible, sheet-like material having a generallyrectangular, elongate configuration when in an extended condition. Thecam includes opposed longitudinal edges 16 and 18. In the preferredembodiment, the cam is a generally rectangular wall of sheet material.The cam can alternatively be of other configurations such as, forexample, a cord-like configuration having a circular or triangularcross-section.

The cam carrier 4 is of greater thickness than the width of the cam 14and has an annular opening 20 (FIG. 2) extending completely about itsperipheral edge into which the projection at the end of the finger 8projects. The cam 14 extends laterally across the opening 20 and issupported therein by aligned, rectangular cross-section guide slots 22and 24 extending into the body of the carrier. The guide slots 22 and 24constitute an elongate guide track having a curvature centered about theaxis of rotation of the cam carrier so they support the wall 14 at acorresponding curvature. In this position the cam has one of its facesexposed to and facing outwardly towards the finger of the sensor.

When the end of the sensor 8 is riding on the surface of the cam 14 itis in a raised condition and when the cam passes beyond the end of thefinger 8, the finger moves radially inward to a depressed conditionthrough a distance at least equal to the thickness of the cam 14. Thesensitivity of the switch contacts is such as to enable this range ofmovement to control the opening and closing of the switch 7.

To enable selective adjustment of the peripheral extent to which the cam14 extends along the guide tracks 22 and 24, the leading end of the cam(in the direction of motion of the cam carrier) is fixedly secured to ahollow, circular hub 26 (FIG. 3). The hub 26 includes a plurality ofinternally serrated axially extending fingers 28 which engage thecorrespondingly serrated external face of a stationary axle 29 (FIG. 2)fixedly secured to the carrier supporting the hub for rotation about anaxis parallel to the cam surface. The hub 26 also includes an annularskirt 30 to which the leading end of the cam is connected in tangentialrelation. The skirt 30 is concentrically spaced about and connected tothe fingers 28 by an annular shoulder portion 32. The skirt is rotatablyreceived within a bore 34 in the cam carrier which assists in supportingthe hub for rotation. The bore 34 has closed axial ends axially abuttingthe shoulder 32 and the free opposite axial end of the hub 26 to centerthe latter axially in the cam carrier. Extending concentrically from thehub 30 in an opposite direction from the fingers 28 is an adjustmentknob 36 projecting through an opening 38 in the cam carrier. For ease ofassembly, the rotary cam carrier 4 is formed from two separate discs 14aand 14b secured together in abutting concentric relation. The discs areinitially separated to enable the hub 26 to be mounted in position inthe bores 34.

By turning the knob 36 manually, the cam 14 can be wound onto and offthe hub 26 to vary the peripheral extent to which the cam extends alongthe guide tracks. It will be understood that the bore 34 has to besufficiently large to accommodate the cam as it is wound onto the hub.In this connection, the skirt 30 includes a depressed region 40 adjacentthe point of connection thereto of the wall 14 to enable the cam tocollapse inwardly against the hub. In addition, the further peripheralportions of the hub 26 extending away from the depressed region 40 mayalso be reduced somewhat out of circularity to accommodate 'thecollapsing thereagainst of the cam within the bore 34 as the cam iswound onto the hub.

The engagement of the serrated fingers 28 with the correspondingserrations on the axle 29 (FIGS. 5 and 6) has a detent action whereby,once the cam has been adjusted to a particular length, the engagingserrations yieldably resist displacement of the hub relative to the axleso that the cam maintains its preselected position. Application oftorque above a predetermined value causes the fingers 28 to be movedapart so that the hub can free itself for rotation. To assist inmaintaining engagement between the serrations on the fingers 28 and theaxle 29, a resilient metal split-ring 42 mounted in a groove embracingthe lower'ends of the fingers 28 is provided. 1

In operation, as one of the cam assemblies moves towards the sensor, thecurved portion of the cam 14 wound about the hub (or if the cam is fullyextended, the hub itself) moves into contact with the projection at thefree end of the finger 8. As the carrier 4 continues to rotate, thecurved surface guides the finger onto the main part of the cam 14,thereby raising the finger 8 and operating the switch 7 to one of itsopen and closed conditions. During continued rotation, as long as thefinger remains in contact with the cam 14, the switch 7 remains in thesame condition. When the trailing end of the cam 14 moves past the endof the finger 8, the finger pivots downwardly through a radial distanceat least equal to the thickness of the cam 14, thereby causing theswitch 7 to operate in the other of its open and closed conditions. Thechange in condition of the switch 7 may be used to perform a controlfunction in. any well-known manner. The switch 7 will remain in thesecond condition until the following one of the cam assemblies 2 reachesthe fingerof the sensor and the switch 7 is again restored to the firstcondition. The switch sensor 6 will then remain in the first conditionfor a further period dependent upon the selected peripheral extent ofthe cam 14 as preselected by rotation of the associated knob 36.

It will be appreciated that with the foregoing arrange ment, the periodsfor which the sensor operates in its first condition can be selectivelyand individually adjusted for each of the different cam assembles. Thus,the structure of the present invention enables a large number ofseparately adjustable cams to be mounted on a single cam carrier. Allthat is necessary is that the cam carrier be made of sufficiently largeradius to accommodate the desired number of individually adjustable camassemblies. In addition, as contrasted with a system based on spacingbetween clips, there is no aggregation or cumulation of periods whichwould require adjustment of each of the downstream positions as isrequired on some prior devices.

To facilitate visual adjustment of each cam, a calibrated scale 50(FIG. 1) extends adjacent each guide track. A pointer 52, comprising aprojecting member secured to the free, rear end of the cam 14 (in thedirection of rotation), registers with the calibrated scale 50. Themovement of the pointer 52 against the scale 50 thus provides an easyvisual reference for adjustment. Where the cam assembly is being usedfor a tim ing function, the maximum time that would be taken to traversebetween the extreme position of adjustment of the cam at a particularrate of rotation of the cam carrier can be determined and the scale 50can be calibrated directly in increments of time.

In the preferred embodiment, the cam 14, hub 26, fingers 28, knob 36 andpointer 52 are molded as an integral structure from a suitable plastic.The mechanical properties of the plastic must be such that the cam 14can bend sufficiently to follow the guide tracks and to wind about thehub, yet it should not be so compliant that it will be unable to resistdeformation at the end of the spring biased finger 8 on the sensor.Suitable plasticsfrom which the wall 14 may be fabricated includepolypropylene, polyethylene, .copolymers of propylene and ethylene, andcertain fluorocarbon polymers, including polytetrafluorethylene "(PTFE),commonly known as Teflon. To assist in maintaining sufficient rigidityof the wall 14, the guide tracks 22 and 24 extend a significant distanceinwardlyfrom the edges of the cam to provide support thereof. Inaddition, at the free, trailing end of the wall 14, it is provided onits opposite side from the sensor with a semicircular strengthening rib53.

Although the invention has thus far been described with reference to amechanical sensor, an adjustable cam assembly according to the inventionmay be used with sensors of other types. Thus, the cam 14 may be used inconjunction with a fluid pressure sensor whereby a jet of fluid isdirected against the cam surface through a nozzle so that as the campasses beyond the nozzle there is a change in pressure which can be usedto provide the control function. Photoelectric sensing may be employedutilizing a light sensor and a photo-detector wherein breaking of alight path causes a change in signal condition or, alternatively,utilizing a refiectively coated cam to provide a reflective. light pathbetween the source and detector which isinterrupted. As a furthermodification, a magnetically coated cam could be used in conjunctionwith a megnetically responsive sensor. In a further. variation, the cammaterial could be impregnated with a low level of radioactivity and thesensor could incorporate ascintillation counter or like device torespond to the passage of the cam past the sensor. Such alternativesensing devices are not intended to be exhaustive and other wellknowncam sensing means may be employed with ,the adjustable cams constructedin accordance with the invention. j

Nor is it necessary that the cam beemployedsolely in a camming systemwhere apluralityof the cams'are moved successively past a single sensor.For example, FIGS. 7 and 8 show a further embodiment of theinvention inwhich a plurality of sensors,.carri ed by a conveyor belt 60,-passsequentially past a single one of the adjustable cams. For example, sucha system could be used in conjunction with objects carriedby the belt tocontrol spraying of each object at a station adjacent the cam for apredetermined length of time dependent on the selected peripheral lengthof the cam.

Summarizing, a cam assembly according to the present invention has theadvantage thata large number of the cam assemblies can be mounted on asingle cam carrier while permitting each cam assembly to be separatelyadjusted withoutrequiring any change in the adjustment of any of theremaining cam assemblies. Additionally, each cam assembly can beadjusted without requiring the use of screw drivers, special settingtools, adhesives or other hard to adjust expedients. More over, each camassembly is mounted in a protected condition within the carrier so thatis is not vulnerable to being knocked off in the same manner that clipsand other projections may be. The provision of a calibrated scale andindicating pointer enables the cam assemblies to be adjusted by personsof average skill without;requiring special competence or the.performance ,of mental calculations prior to adjustment of camposition. It is also advantageous that the cam assembly can readily bemolded from inexpensive plastic materials thereby providing a structurewhich lends itself to low cost production and ease of fabrication.

Although the invention has been described with reference to certainpreferred embodiments, it will be understood by thoseskilled in the artthat many deletions, additions, substitutions, modifications, I andother changes may be made which will fall within the spirit of theinvention disclosed and claimed herein.

We claim:

1. For use in a camming system including a sensor and a cam carriermounted for motion relative to each other along a predetermined path ofmotion, an adjustable cam assembly comprising:

an elongate guide track on the carrier;

an elongate flexible cam movable along said guide track, said cam havingopposite longitudinal ends, said guide track supporing said cam with atleast a longitudinally extending portion of said cam exposed to andfacing towards the sensor to be sensed thereby when proximate to thesensor.

a hub fixedly secured to one longitudinal end of said cam; and

mounting means for rotatably mounting said hub on the carrier to enablesaid cam to be selectively would onto and off said hub to vary thelongitudinal exent of the portion of said cam exposed to the sensor.

2. An adjustable cam assembly as defined in claim 1, wherein said hubhas a central bore concentric with the axis of rotation of said hub andwherein said mounting means comprises a stationary axle fixedly securedto the carrier extending concentrically into said bore to support saidhub for rotation.

3. An adjustable cam assembly as defined in claim 2,

further including:

detent means for yieldably resisting rotational movement between saidhub and said axle.

4. An adjustable cam assembly as defined in claim 3,

wherein said detent means includes:

a plurality of serrations on said axle;

a plurality of fingers connected to said hub extending in overlappingcontact with said axle spaced around the periphery thereof to supportsaid hub for rotation on said axle, said fingers having serrationsbiased into engagement with the serrations on said axle, said fingersflexing radially outwardly to cause said serrations to move out ofengagement to enable turning of said hub when torque in excess of apredetermined value is applied thereto.

5. An adjustable cam assembly as defined in claim 4,

further including:

a resilient split ring connected with said fingers for resilientlybiasing said fingers against said axle.

6. An adjustable cam assembly as defined in claim 2,

' further including:

an adjustment member projecting from said hub at an end thereof remotefrom said carrier, said adjustment member adapted to be grasped to turnsaid I: .hub relative to said carrier for adjustment of the :length ofsaid portion of said cam exposed to the sensor. t 7. An adjustable camassembly as defined in claim 1,

.wherein the sensor remains stationary and said cam is carried past thesensor by the cam carrier along the 9. A camming system comprising:

a sensor;

a cam carrier, said cam carrier and said sensor being connected witheach other for relative motion therebetween along a predetermined pathof motion;

an elongate guide track on the carrier;

an elongate flexible cam movable along said guide track, said cam havingopposite longitudinal ends, said guide track supporting said cam with atleast a longitudinal portion of said cam exposed to and facing towardsthe sensor to be sensed thereby;

a hub fixedly secured to one of said longitudinal ends of said cam; and

mounting means for rotatably mounting said hub on said carrier to enablesaid cam to be selectively wound onto and off said hub to decrease andincrease the longitudinal extent of the portion of said cam exposed tosaid sensor.

10. A camming system as defined in claim 9, wherein said sensor sensessaid cam by mechanical contact.

11. A camming system as defined in claim 9, wherein said sensor sensessaid cam photoelectrically.

12. A camming system as defined in claim 9, wherein said sensor sensessaid cam by fluid pressure.

13. A camming system as defined in claim 9, wherein said sensor sensessaid cam magnetically.

14. A camming system as defined in claim 9, wherein said sensor sensessaid cam by detection of radioactivity.

15. A camming system, comprising: a frame; a rotary cam carrier mountedon said frame for rotation thereon, said cam carrier being divided alongits periphery into a plurality of sectors; a plurality of cam assemblieseach connected with one of said sectors, each said cam assembly includ-1n an elongate guide track on said carrier. an elongate flexible cammovable along said guide track, said guide track supporting said camwith at least a peripherally extending, exposed portion of said camfacing outwardly from said carrier,

varying means for selectively varying the peripheral extent of saidexposed portion of said cam; and

a sensor mounted on said frame for sensing the exposed portion of eachsaid cam as each of said cam assemblies moves past said sensor duringrotation of said cam carrier.

16. A camming system as defined in claim 15,

wherein for each said cam assembly:

each said cam has opposite longitudinal ends spaced peripherally of saidcarrier;

and wherein each said varying means includes:

a hub fixedly secured to one of said longitudinal ends of the associatedone of said cams; and

mounting means for rotatably mounting said hub on said carrier to enablethe associated said cam to be selectively wound onto and off said hub todecrease and increase the longitudinal extent of the outwardly facingexposed portion thereof, respectively.

17. A camming system as defined in claim 16, wherein said sensorincludes a finger biased downwardly into the path of travel of said camssuccessively past said sensor, each of said hubs being positioned at theleading end of the associated said cam in the direction of movementthereof past said sensor and being curved to guide and raise said fingeronto said cam as said cam passes beneath said sensor.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORREQTION PATENTNO.:3,885,470

ATED D May 27, 1975 |NVENTOR(S) Robert Costa et a1.

It is certified that error appears in the ab0ve-identified patent andthat said Letters Patent are hereby corrected as shown below:

Colume 1, line 57, "chanting" should be canting Colume 2 line 25, after"surface" the word exposed i is omitted.

Colume 5, line 52, "position" should be positions Colume 6, line 3,"thereof" should be therefor Colume 6, line 53, after "that", "is"should be is Colume 7, line 11, "supporing" should be supporting Signedand Erealed this fourteenth D 3.) 0 f October 1 9 75 [SEAL] Attest:

RUTH C. MrtSON C. MARSHALL DANN Arresting Officer Commissioner ofPatents and Trademarks UNITED STATES PATENT OFFICE CERTIFICATE OFCORRECTION PATENT NO. 3,885,470

DATED May 27, 1975 INVENTOIKS) I b t B. C -ta e't al.

It is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

Colume 1, line 57, "chanting" should be canting Colume 2, line 25, after"surface" the word exposed is omitted.

Colume 5, line 52, "position" should be positions Colume 6, line 3,"thereof" should be therefor Colume 6, line 53, after "that", "is"should be is Colume 7, line 11, "supporing" should be supporting Signedand Sealed this fourteenth D ay of October 1975 [SEAL] A ttest:

RUTH C. MRSON p C. MARSHALL DANN Arresting Officer CommissionerufParents and Trademarks

1. For use in a camming system including a sensor and a cam carriermounted for motion relative to each other along a predetermined path ofmotion, an adjustable cam assembly comprising: an elongate guide trackon the carrier; an elongate flexible cam movable along said guide track,said cam having opposite longitudinal ends, said guide track supporingsaid cam with at least a longitudinally extending portion of said camexposed to and facing towards the sensor to be sensed thereby whenproximate to the sensor. a hub fixedly secured to one longitudinal endof said cam; and mounting means for rotatably mounting said hub on thecarrier to enable said cam to be selectively would onto and off said hubto vary the longitudinal exent of the portion of said cam exposed to thesensor.
 2. An adjustable cam assembly as defined in claim 1, whereinsaid hub has a central bore concentric with the axis of rotation of saidhub and wherein said mounting means comprises a stationary axle fixedlysecured to the carrier extending concentrically into said bore tosupport said hub for rotation.
 3. An adjustable cam assembly as definedin claim 2, further including: detent means for yieldably resistingrotational movement between said hub and said axle.
 4. An adjustable camassembly as defined in claim 3, wherein said detent means includes: apluraality of serrations on said axle; a plurality of fingers connectedto said hub extending in overlapping contact with said axle spacedaround the periphery thereof to support said hub for rotation on saidaxle, said fingers having serrations biased into engagement with theserrations on said axle, said fingers flexing radially outwardly tocause said serrations to move out of engagement to enable turning ofsaid hub when torque in excess of a predetermined value is appliedthereto.
 5. An adjustable cam assembly as defined in claim 4, furtherincluding: a resilient split ring connected with said fingers forresiliently biasing said fingers against said axle.
 6. An adjustable camassembly as defined in claim 2, further including: an adjustment memberprojecting from said hub at an end thereof remote from said carrier,said adjustment member adapted to be grasped to turn said hub relativeto said carrier for adjustment of the length of said portion of said camexposed to the sensor.
 7. An adjustable cam assembly as defined in claim1, wherein the sensor remains stationary and said cam is carried pastthe sensor by the cam carrier along the predetermined path of motion. 8.An adjustable cam assembly as defined in claim 1, wherein a calibratedscale is provided on the carrier extending adjacent said guide track andwherein said cam at the opposite longitudinal end thereof is providedwith a pointer aligned with said graduated scale for indicating theposition of said opposite end of said cam relative to said scale duringwinding and unwinding of said cam about said hub.
 9. A camming systemcomprising: a sensor; a cam carrier, said cam carrier and said sensorbeing connected with each other for relative motion therebetween along apredetermined path of motion; an elongate guide track on the carrier; anelongate flexible cam movable along said guide track, said cam havingopposite longitudinal ends, said guide track supporting said cam with atleast a longitudinal portion of said cam exposed to and facing towardsthe sensor to be sensed thereby; a hub fixedly secured to one of saidlongitudinal ends of said cam; and mounting means for rotatably mountingsaid hub on said carrier to enable said cam to be selectively wound ontoand off said hub to decrease and increase the longitudinal extent of theportion of said cam exposed to said sensor.
 10. A camming system asdefined in claim 9, wherein said sensor senses said cam by mechanicalcontact.
 11. A camming system as defined in claim 9, wherein said sensorsenses said cam photoelectrically.
 12. A camming system as defined inclaim 9, wherein said sensor senses said cam by fluid pressure.
 13. Acamming system as defined in claim 9, wherein said sensor senses saidcam magnetically.
 14. A camming system as defined in claim 9, whereinsaid sensor senses said cam by detection of radioactivity.
 15. A cammingsystem, comprising: a frame; a rotary cam carrier mounted on said framefor rotation thereon, said cam carrier being divided along its peripheryinto a plurality of sectors; a plurality of cam assemblies eachconnected with one of said sectors, each said cam assembly including, anelongate guide track on said carrier. an elongate flexible cam movablealong said guide track, said guide track supporting said cam with atleast a peripherally extending, exposed portion of said cam facingoutwardly from said carrier, varying means for selectively varying theperipheral extent of said exposed portion of said cam; and a sensormounted on said frame for sensing the exposed portion of each said camas each of said cam assemblies moves past said sensor during rotation ofsaid cam carrier.
 16. A camming system as defined in claim 15, whereinfor each said cam assembly: each said cam has opposite longitudinal endsspaced peripherally of said carrier; and wherein each said varying meansincludes: a hub fixedly secured to one of said longitudinal ends of theassociated one of said cams; and mounting means for rotatably mountingsaid hub on said carrier to enable the associated said cam to beselectively wound onto and off said hub to decrease and increase thelongitudinal extent of the outwardly facing exposed portion thereof,respectively.
 17. A camming system as defined in claim 16, wherein saidsensor includes a finger biased downwardly into the path of travel ofsaid cams successively past said sensor, each of said hubs beingpositioned at the leading end of the associated said cam in thedirection of movement thereof past said sensor and being curved tO guideand raise said finger onto said cam as said cam passes beneath saidsensor.